(a) Field of the Invention
The present invention relates to an electrode composition for a supercapacitor, an electrode including a cured material, and a supercapacitor including the electrode.
(b) Description of the Related Art
A capacitor is one of energy storage devices. The capacitor storages electricity by forming a charge ion layer at both ends of an electrode, when a dielectric material is positioned between two metal plates which are apart by a predetermined distance, and the voltage is applied. At this time, the electricity may be simply generated by an electric double layer, rather than the chemical reaction which generates the electricity in batteries. Accordingly, the electrode is not damaged during the electricity generation of the capacitor, so that it has an almost unlimited cycle-life characteristic. Furthermore, times for charging and discharging are not long so that a large amount of current may be stored for a short time. Therefore, the capacitor is an important electricity storage device when high power is required.
The capacitor has one disadvantage relating to poor electricity storage ability. The storage capacity of the capacitor is inversely proportional to the distance between the two plates and is proportional to the area of the two plates. Therefore, the storage capacity may be increased by increasing an area of the electrodes if the distance is fixed. However, there is no advantage in merely increasing the apparent surface areas since it causes an increase in volume of the device, so it is necessary to increase effective areas. The effective areas may be generally increased by forming minute pores in the electrode.
Thus, the disadvantage may be addressed by using a porous material having a large effective area and having low electric resistance as an electrode material. Furthermore, it is required for the material that good conductivity allows to reduce Joule's heat, thereby lowering energy consumption. Active carbon may be conventionally used as the material to satisfy the above requirements. Active carbon has a large effective surface since it has abundant pores formed during carbonization, and has good conductivity so that it is widely used in the industrial purposes.
The supercapacitor is a capacitor (condenser) of which the electrical capacity is mainly improved and is used as a battery. The capacitor used in an electronic circuit acts as a rechargeable battery. That is, the capacitor is used to store electricity and to emit, if necessary, and is an essential component for stable working of an electronic circuit.
The supercapacitor includes electrodes and an electrolyte layer between the electrodes, and forms an electric double layer on the electrode and the electrolyte.
The electrode includes active carbon as a main component, and active carbon includes a carbonaceous material with an extreme high surface area and has suitable structure to form the electric double layer with ions of the electrolyte due to the high surface area and the electrical conductivity of the carbon itself.
However, the active carbon generally has a hydrophobic property at the surface of the carbon. The electrode includes a hydrophobic polymer binder such as polyvinylidene fluoride, and the electrolyte has a hydrophilic property since it has water-solubility. Thus, it is difficult to form an effective electric double layer.
Studies for forming an effective electric double layer are investigated by bonding hydrophilic functional groups such as —COOH, —OH, etc., to a surface of the active carbon to prepare a functional active carbon.
However, the functional active carbon has disadvantages in that it may be easily dissolved in the water-solubility electrolyte, since it has hydrophilicity at a surface.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.